Cigarette with increased self-extinguishing tendency

ABSTRACT

A cigarette with an increased self-extinguishing tendency, wherein the cigarette paper has annular zones whose porosity is reduced by the presence of a polymer, whose interfacial tension is over 33 mJ/m 2 .

FIELD OF THE INVENTION

[0001] The invention relates to a cigarette with an increasedself-extinguishing tendency, wherein the cigarette paper has annularzones whose porosity is reduced by the presence of a polymer.

BACKGROUND OF THE INVENTION

[0002] In recent years, in particular in the USA, there has been anincreasing demand that cigarettes which are left lying aroundunextinguished should not set fire to combustible materials and in thisrespect in particular textiles (carpets). Although objectively the riskof corresponding accidents is not very high, a series of proposals havebeen put forward as to the way in which cigarettes are left lying aroundwhile burning can be caused to be quickly extinguished.

[0003] The proposal disclosed in EP 0 864 259 can be viewed as typicalin respect of the state of the art. Here a cellulose polymer innon-aqueous solution is applied to the cigarette paper in the form ofrings which are spaced from each other. The paper is of reduced porosityin the region of those rings and the cigarette goes out when burning ofthe cigarette has progressed as far as that ring. There is a recognisedstandard for the self-extinguishing tendency of cigarettes, morespecifically the NIST test (NIST Technical Note 1436 App. D).

SUMMARY OF THE INVENTION

[0004] The object of the invention is on the one hand to satisfy thedemands of that test and on the other hand to avoid the disadvantages ofthe state of the art.

DETAILED DESCRIPTION OF THE INVENTION

[0005] They are considered in particular to be that the cellulosederivatives applied to the paper, fillers or highly ground fibres, format the surface of the cigarette a film, in the region of which thethickness of the coated paper is markedly increased. In comparison theaim is to find a material in which the desired self-extinguishingtendency is not achieved by an external film but by altering the paperstructure in the printed region. In itself it was not to be assumed thatthe actually hydrophobic polymers penetrate into the hydrophilic paper.It is found however that, when the interfacial tension of the polymersused is in the proximity of that of regenerated cellulose, the polymerpenetrates into the cavity structure of the paper without a desired filmformation occurring at the surface. It is advantageous in that respectif the polar proportion of the interfacial energy is as high aspossible. It is therefore essential for the invention that theinterfacial tension of the polymer is over 33 mJ/m².

[0006] Inter alia polyvinyl acetate, partially hydrolysed polyvinylacetate or polyvinyl alcohol have proven to be particularly suitable.Polyvinyl acetate is polar and its interfacial tension is 36.5 mJ/m².Non-polar ethyl cellulose at 32 mJ/m² in contrast is as discussedfilm-forming and cannot be used in accordance with the invention (allfigures from: Polymer Data Handbook, 1999, Oxford University Press Inc).

[0007] It will be appreciated that it is necessary for the selectedpolymer to be applied in a sufficient amount and in a condition ofsuitable geometrical distribution in order to satisfy the criteria ofthe NIST test. As regards distribution of the bands, a width of morethan 4 mm is desirable, even if not critical. It will be appreciatedthat the bands which stop the cigarette from burning may also not bedisposed at excessively great distances, for which reason thosedistances are preferably below 20 mm.

[0008] As regards the applied amount of polymer, simple tests make itpossible to establish the values as from which the self-extinguishingtendency is sufficient. In that respect note is to be taken of thesurprisingly established fact that a great reduction in porosity stilldoes not automatically result in a substantially improvedself-extinguishing tendency. It is only a further incorporation ofmaterial into the paper that leads to an almost abrupt increase in theself-extinguishing tendency. In this connection, attention is directedmore specifically to the examples set out hereinafter.

[0009] The way in which the polymer is introduced into the paper is notcritical, but intaglio printing has proven to be appropriate. By virtueof using intaglio printing the bands have a high level of edgesharpness, and it is not possible to detect a steady increase in theapplication of material from the edge to the centre. The amount appliedis adjusted by virtue of the etching depth, the pattern repeat, thelevel of concentration and the viscosity of the printing solution.

[0010] In order to improve the opacity of the paper, it is possible touse fillers such as aluminium hydroxide, magnesium hydroxide or titaniumoxide in the printing solution. Those fillers however have no measurableinfluence on the self-extinguishing tendency of cigarettes.

[0011] The invention is described in greater detail hereinafter byreference to examples.

EXAMPLE 1

[0012] Bands 6 mm in width are printed at a spacing of 19 mm oncigarette paper with an initial porosity of 38 CU by means of intaglioprinting with a solution of 35% of polyvinyl acetate in ethyl acetate(discharge viscosity 4 mm=18 s).

EXAMPLE 2

[0013] Bands 7 mm in width are printed at a spacing of 20 mm oncigarette paper with an initial porosity of 38 CU by means of intaglioprinting with a solution of 350/% of polyvinyl acetate in ethyl acetate(discharge viscosity 4 mm=18 s).

EXAMPLE 3

[0014] Bands 6 mm in width are printed at a spacing of 19 mm oncigarette paper with an initial porosity of 38 CU by means of intaglioprinting with a solution of 350/% of polyvinyl acetate in ethanol(discharge viscosity 4 mm=20 s).

EXAMPLE 4

[0015] Bands 6 mm in width are printed at a spacing of 19 mm oncigarette paper with an initial porosity of 50 CU by means of intaglioprinting with a solution of 35% of polyvinyl acetate in ethyl acetate(discharge viscosity 4 mm=18 s).

EXAMPLE 5

[0016] Bands 6 mm in width are printed at a spacing of 19 mm oncigarette paper with an initial porosity of 38 CU by means of intaglioprinting with a solution of 31% of polyvinyl acetate and 7% of aluminiumhydroxide in ethyl acetate (discharge viscosity 4 mm=21 s).

EXAMPLE 6

[0017] Bands 6 mm in width are printed at a spacing of 15 mm oncigarette paper with an initial porosity of 38 CU by means of intaglioprinting with a solution of 23% of polyvinyl acetate in ethyl acetate(discharge viscosity 4 mm=23 s).

EXAMPLE 7

[0018] Bands 6 mm in width are printed at a spacing of 15 mm oncigarette paper with an initial porosity of 38 CU by means of intaglioprinting with a solution of 20% of polyvinyl acetate and 8% of aluminiumhydroxide in ethyl acetate (discharge viscosity 4 mm=25 s).

[0019] Results:

[0020] The paper is cut into 27 mm wide coils or bobbins. Kingsizefilter cigarettes are produced therefrom. No. Application mg/cm² CU inthe band SE % (NIST))** Untreated 0 —)* 0 Example 1 0.73 4.3 100 Example2 0.73 4.4 100 Example 3 0.73 8.1 60 Example 4 0.80 5.5 95 Example 50.82 5.0 100 Example 6 0.17 3.2 10 Example 7 0.25 4.8 5

[0021] Examples 6 and 7 confirm the point set out in the opening part ofthis specification that a reduction in permeability as measured inCoresta Units (CU) still does not guarantee an adequateself-extinguishing tendency. On the contrary the latter is to bemeasured directly and the application amount is to be increased untilthe desired result is attained.

1. A cigarette with an increased self-extinguishing tendency, whereinthe cigarette paper has annular zones whose porosity is reduced by thepresence of a polymer, characterised in that the interfacial tension ofthe polymer is over 33 mJ/m².
 2. A cigarette according to claim 1characterised in that the interfacial tension is between 36 and 42mJ/m².
 3. A cigarette according to claim 1 characterised in that thepolymer includes at least one of the compounds polyvinyl acetate,partially hydrolysed polyvinyl acetate or polyvinyl alcohol.
 4. Aprocess for producing cigarettes according to claim 1 characterised inthat the polymer dissolved in organic solvent is applied to thecigarette paper by an intaglio printing process and penetrates for thepredominant part thereof into the cigarette paper.
 5. A cigaretteaccording to claim 2 characterised in that the polymer includes at leastone of the compounds polyvinyl acetate, partially hydrolysed polyvinylacetate or polyvinyl alcohol.